Automatic switching system



Sept. 8, 1953 P. c. BOREL EIAL AUTOMATIC swncamc SYSTEM 19 Sheets-Sheet 2 Filed May 11, 1950 m m m m M 5 PR m H w m u 0k H n h m w a 00000 0 h m x 0002 4 0 N wot C Attorney P 1953 P. c. BOREL ETAL 2,651,681

AUTOMATIC SWITCHING SYSTEM Filed May 11, 1950 19 Sheets-Sheet 3 q Q I Inventors PI RE 6. BOREL Attorney Sept. 8, 1953 P. c. BOREL ETAL 2,651,681

AUTOMATIC SWITCHING SYSTEM 1 Filed May 11, 1950 19 Sheets-Sheet 4 Inventors PIERRE a. 30x54 MARtEL R. MAUGE Sept. 8, 1953 P. c. BOREL ETAL 2,651,681

AUTOMATIC SIITGHING sYs'rEu Filed lay 11, 1950 19 Sheets-Sheet 5 Q U Q u Inventors PIERRE c. can MARCEL R. mass By v A ttom ey p 1953 P. c. BOREL ETAL 2,651,681

AUTOMTIC SWITCHING SYSTEM Filed May 11, 1950 19 Sheets-Shet s Inventor: Helm: -c. MEL IMRCEL R, M114 Se t. 8, 1953 P. c. BOREL EI'AL 2,651,531

Auqroumrxc surcamc SYSTEM Filed an 11, 1950 I 19 Sheets-Sheet 7 F/GZ Inventors PIERRE c. sak mncel. R. MAuqE By A llomcy Sept. 8, 1953 P. c. BOREL EI'AL AUTOMATIC swrrcamc SYSTEM 19 Sheets-Sheet 8 Filed llay 11, 1950 E 0 6 R0 mam m m M r: 8 s Mun Sept. 8, 1,953

P. C. BOREL ETAL AUTOMATIC SWITCHING SYSTEM Filed May 11, 1950 19 Sheets-Sheet 9 Inventors PIERRE c. aMEL MARcEL R. MAI/6E P 1953 P. c. BOREL ETAL 2,651,681

AUTOMATIC smcnmc svs'rm Filed May 11, 195Q 19 Sheets-Sheet 10 Fig. 4.

Inventors Hem: c. BOREL MAML R. M4065 8, 1953 P. c. BOREL EIAL 651,681

AUTOMATIC SWITCHING SYSTEM Filed May 11, 1950 19 Sheets-Sheetll Fig.4.

I nvenlors PIERRE c. BOREL MARcEL R. MAI/6E Sept. 8, 1953 P. c. BOREL ETAL AUTOMATIC swncumc SYSTEM 19 Sheets-Sheet 12 Filed May 11, 1950 Inventors PIERRE C- BDREL R- MAI/GE MARCE L Attorney Sept. 8, 1953 P. c. BOREL ETAL AUTOMATIC smcumc; SYSTEM 19 She ets-Sheet 13 Filed May 11, 1950 Inventors PIERRE c. BOREL MARCEL R- MAl/fiE p 8, 1953 P. c. BOREL ETAL 2,651,681

' AUTOMATIC SWITCHING SYSTEM Filed May 11, 1950 19 Sheets-Sheet -15 Inventors PIEERE c. BOREL MEL R. MUQE Attomiy p 8, 1953 P. c. BOREL ETAL 2,651,681

AUTOMATIC SWITCHING SYSTEM Filed May 11. 1950 19 Sheets-Sheet 16 FIG/6.

Inventors PIERRE c. BOREL MARCEL R- MAI-16E Atlor ney Se t. 8, 1953 P. c. BOREL ETAL 2,651,681

AUTOMATIC SWITCHING SYSTEM Filed May 11, 1950 19 Sheets-Sheet 19 L Q N Q L; Inventors PIERRE G. BOREL HARCEL R..MAUGE llorney Patented Sept. 8, 1953 AUTOMATIC SWITCHING SYSTEM Pierre Charles Borel and Marcel Roger Mauge,

Boulogne-Billancourt, France, assignors to International Standard Electric Corporation, New

York, N.

Y., a corporation of Delaware Application May 11, 1950, Serial No. 161,396 In France May 12, 1949 3 Claims. 1

The present invention relates to improvements in automatic switching systems used for instance in telephone exchanges, and particularly in automatic switching systems utilizing electrical marking characteristics.

One of the objects of the present invention is to provide a switching system wherein the required switching equipment is greatly reduced so as to minimize installation and maintenance expenses.

Another object of the present invention is to provide a switching mechanism permitting a rapid execution of switching operations such as to reduce equipment expenses.

According to one feature of the present invention there are provided in an automatic switching system, test means adapted to determine both the availability and characteristic of a circuit, simultaneously.

In accordance with the present invention, in

order to ascertain whether a circuit has been reached by two difierent selector switches, there is provided switching means operative on one hand to disconnect a high value resistance connected after a free circuit is tested and to connect in place of this resistance a low value resistance. The potential difference at the terminals of this low value resistance is utilized to bias the grid of a vacuum tube, the cathode of which is brought to such a potential that the tube is blocked if only one selector switch has .reached the desired circuit and unblocked if two selector switches have reached the circuit. In addition a cold cathode tube is provided, the anode of the vacuum tube being connected in one condition to the positive terminal of a high voltage source through a resistance, and in another condition to the control grid of the cold cathode tube which ionizes when said vacuum tube is blocked. A relay is provided, the winding of which is connected in series in the main anode circuit of said cold cathode tube the relay being arranged to control switching means inthe register to control a new hunting operation in case of a double test.

The basic automatic switching arrangement in one embodiment of the present invention does not use any line relay or cut-oif relay. When a subscriber closes the line circuit, a current flow is caused, which at a suitable point is used to characterize the state of the line, and in particular to cause the starting operation. In the embodiment considered, the negative terminal of a battery is connected to one of the ends of a 30,000 ohm resistance, the other end of said resistance being connected through a 15,000 ohm resistance to one of the line wires, while the other line wire is connected through a 15,000 ohm resistance to the positive terminal of the battery. Under such conditions, the potential difference at the terminals of the 30,000 ohm resistance is of about 24 volts when the line is calling;

The wire connected to the common point of 30,000 ohm resistances is brought to a potential of approximately -24 volts. The starting circuit is arranged to control the hunting for the calling line as soon as the potential of the wire is more than 35 volts. In the event in which a line presents an insulation lower than a predetermined value, for example 50,000 ohms, it is possible that, even when the line is not calling, the potential applied to the wire will be sufficiently near the calling potential to cause a false starting operation.

The present invention discloses an arrangement to prevent these disadvantages by providing a line circuit including a cut-off relay which is specially adopted to be used in conjunction with the basic switching system hereinafter described.

In accordance with this modification there is provided means used to disconnect said resistances from the line wires as soon as the calling line is connected to a line finder, the control of said means being effected directly by means of the potentials existing on the line wires as soon as the line finder is connected to said line wires.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood, by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

Figure 1 represents in block form the manner of joining certain of the drawings to form the circuitry of a described embodiment of the invention;

Figure 2 shows a. well know line circuit without line and cut-oil relays;

Figure 3 shows the starting circuit which completes the circuitry of Fig. 2, the circuit of Fig. 3 being common to a group of subscribers lines;

Figure 4 illustrates a line finder circuit;

Figure 5 illustrates a' connector circuit used in the present embodiment of the invention;

Figure 6 illustrates a group selector circuit;

Figure 7 illustrates a final selector circuit; 

